جستجوی مقالات مرتبط با کلیدواژه "قاب بتنی" در نشریات گروه "عمران"

Piezoelectric materials are a type of smart materials that are of interest to many researchers in various engineering sciences due to their extraordinary properties such as converting mechanical energy into electrical energy and vice versa. In this article, the determination and control of the dynamic deformation of a one-span concrete frame with a piezoelectric layer coating on beams and columns under seismic load is discussed. In order to control the dynamic deformation of the concrete frame, a proportional-derivative controller has been used in such a way that a piezoelectric layer is considered as an actuator and a layer as a sensor. The governing equations for the beam and column components of concrete frame are obtained by using high-order shear theory, calculating energy relations, applying Hamilton's principle and considering the applied voltage on piezoelectric materials. In order to solve the dynamic coupled equations, the numerical method of differential quadrature method has been used and finally, with the help of Newmark method, the dynamic deformation of the concrete frame is calculated. After validating the results, the effect of various parameters such as voltage applied to the piezoelectric layer, piezoelectric type controller, thickness of the piezoelectric layer on dynamic deformation were investigated. Here, the optimal values of controller parameters, including proportionality coefficient and derivative coefficient, were obtained as 3.824 and 5.812, respectively. The results show that the use of the controller leads to a reduction of 72 and 65 percent of the lateral and vertical dynamic deflection of the frame, respectively.

Using steel shear walls is one way to increase the lateral load-carrying capacity of reinforced concrete moment-resisting frames and have been gaining the interest of researchers due to their excellent performance in earthquakes and ease of construction. In these shear walls, connection to the frame and force transfer between the wall and the frame are of particular interest. In this study, the connection type of these walls and transfer of forces between them and the frame via bolts were examined and controlled using the ABAQUS software. For this purpose, a two-story concrete frame equipped with steel shear walls was evaluated after verifying the numerical model. The frame was assessed under two connection conditions: the ideal state, in which the shear wall is fixed to the beam, and the realistic state, in which these shear walls are attached to the beam using connecting plates on the beams and bolts at the top and bottom of the beam. To design the bolts, first, the prestressing force needed to prevent sliding should be calculated, according to which the prestressing force and the bolts can be designed. Also, the simultaneous effect of tension and shear should be taken into account in the bolts design. .After designing the bolt diameter and prestressing force, the behaviors of the frame were compared in both cases. The numerical analysis revealed that the load-displacement behaviors in both cases were almost identical. Furthermore, the stress in the bolts in the second state was found to be lower than their strength, indicating that the bolt design method is safe and suitable for transferring forces between the shear wall and the reinforced concrete structural frame in floors. Also, by designing the bolt and its prestressing force according to the method of this paper, it is ensured that no slippage between the concrete and the connection plates occurs until the end of loading.

The steel shear wall is an efficient lateral load-bearing system for steel and concrete structures. These members have been gaining interest because of advantages such as high stiffness, fewer architectural limitations, light weight, and lower footprint in plan. When shear walls are used in a semi-continuous state in the structure, it is possible to consider an opening in the span without creating a hole in the shear wall. In the present study, numerical research was performed on the behavior of concrete frames containing a steel shear wall with a semi-continuous connection to the frame. First, the numerical model was validated using an experimental specimen. Then, by performing 33 nonlinear static analyses, the effect of the wall width and thickness on the seismic behavior of concrete frames was investigated. Similarly, the width of the wall was considered to vary from 10 to 110 cm in 11 cases. In addition, the shear wall thickness was examined in 3 cases of 1, 2 and 3 mm, respectively. The outputs of the frame included energy loss, lateral stiffness, strength, and ductility of the frame. To calculate the shear wall stiffness, a formula was presented using the curve fitting technique based on numerical results. By using this formula, the wall stiffness can be estimated with good accuracy using its width and thickness. After comparing the results, it was observed that when the shear wall width in the frame was selected correctly, not only the stiffness and lateral strength of the frame increased, energy loss and ductility of the frame were 2.7 and 1.7 times those of the plain frame, respectively. By considering the ratio of the shear wall width to the frame span equal to 0.38, a proper width can be obtained for the shear wall.

In recent years, Coupled Steel Plate Shear Wall system has been used in mid and high-rise buildings because it has advantages such as providing large spaces for creating various uses. So this was brought into the attention of the designers. The lateral structural response is exactly dependent on the shear walls behavior; therefor these elements must response well under different loading situation. So this paper aims to study the effects of near and far fault earthquakes on the two series of mid-rise frame with the steel plate shear wall with the coupling system. In both series, the coupled steel plate shear wall will be evaluated by variation of opening dimensions, one in length of 1 and 2 m and the width of 0.6 m and 0.9 m with regularity in the plan. Firstly, structures are modeled in ETABS software three dimensionally. Then, the axis frame is analysed in OpenSees two dimensionally. In this paper, the nonlinear static pushover and dynamic time history analyses are carried out. The results of nonlinear analyses show that by increasing the dimensions of the openings, the drift and absolute displacement of the stories are enhanced and also by decreasing the dimensions of the openings, the amount of stories shear and base shear are decreased, which indicates the great effect of the dimensions of the openings on the seismic behavior of coupled steel plate shear wall with considering the performance levels of the frame.

Nowadays, finding ways to reduce earthquake force due to its damages is one of the most important challenges in the field of earthquake engineering. As a result, the selection of passive Viscouz damper is preferable due to its low cost advantage, more appropriate technology and commen use in country. In this research, the effect of Viscouz damper on seismic performance of concrete moment resisting frame has been investigated. For this purpose, three medium concrete moment resisting frames, which have3, 6 and 10-floors, are designed by the Sap2000 software without damper effect. Then, the damper has been analyzed by siesmo struct software. these frames have been designed by common methods, and then have been studied under the acceleration of selected earthquake mappings by using static pushover and dynamic time history analysis, with and without supplemental viscous dampers. Based on these studies, a value is suggested for the behavior factor of the damper added to the structure and compared with the values contained in the 2800 regulations. Also, this factor is investigated in structures equipped with this damper in far field and near field earthquakes. by including viscous damper, damping increases 20% .the suggested values of the behaviour factor for the static pushover and dynamic time history analysis are 6.29 and 6.23 respectively.

This paper presents an experimental study of steel plate shear wall in the concrete moment frame. This study was based on the idea of using steel plate shear walls in precast concrete structures. The steel plate shear wall was bolted to the embedded plates in concrete boundary elements. These plates were embedded at specified intervals, and friction connection was used for the bolted connections. Semi-static cyclic loading was applied to three different specimens according to ACI T1.1-01 code. Lateral load was applied to the top of specimens. The formation of tension field and buckling waves expressed the required behavior of steel shear walls and, also, good performance of connection scheme. In order to illustrate the effects of adding steel shear plate wall to a concrete frame, one of the specimens was considered to be a bare frame. The results showed the placing of steel shear plate wall in the concrete frame, multiplied loading capacity, initial stiffness, dissipated energy, and equivalent damping of the bare frame by three, eight, twelve, and four, respectively. Horizontal and vertical stiffeners decreased the effects of openings. As diagonal opening with horizontal and vertical stiffeners kept initial stiffness the same and increased dissipated energy and equivalent damping by about 15\%; however, the lateral capacity decreased by 7\%. The results of the strain gauge showed that yielding initiated at a 0.4\% drift level. For the simple steel plate shear wall, the yielding started from corners; for the specimen with openings and stiffeners, it started from the bottom solid panel connected to beam and, also, edges of openings. The stress intensity of the bottom solid panel was more than the rest. Moreover, the steel plate initiated tearing at a drift level of 1.75\%. According to the strain gauge results, embedded corners plates were critical; however, all of them remained elastic. Moreover, it could be said that dissipated energy was obtained from steel plate shear wall. Small bending and shear cracks occurred at the beam-column connection. All of the specimens failed given hinge supports of columns.

In the recent years، attempts have been made to prove effectiveness of FRPs in retrofitting/repairing of the reinforced concrete (RC) components. The use of fiber-reinforced polymers (FRP) to create composite concrete structures has increased in recent years. However، the seismic performance of RC structures retrofitted using FRP composites is yet to be scrutinized in terms of improving strength، ductility. This is of high importance if the retrofitted structures are to withstand higher seismic ground motions. The purpose of this study was to investigate the seismic performance of RC joint in frame structures under cyclic lateral loading. Analytical calculations using a finite element method (FEM) are presented for the strength، crack pattern; behavior of frames strengthened with layers of FRP and an experimental study of firth and third author of this paper is carried out to verify the mechanical properties of the proposed. The specimens were tested in a 3D test frame in structure laboratory of civil and environmental engineering department in AmirKabir University of Technology. Analytical models were investigated in LS-DYNA environment. Three test specimens were constructed and tested under cyclic lateral loading. Three-dimensional nonlinear finite element models for the RC frames were developed and simulated with the LS-DYNA finite element analysis (FEA) software. Three 1/3 scaled one-bay and one-storey. Frame designed was carried out based on ACI318 code. These specimens were typical as-built frames abstracted from the existing middle-rise residential buildings in Iran. Two specimens were reinforced by CFRP at the ends of beams، columns and at the joints; one specimen the other specimen was not reinforced and was used for comparison. The retrofitted specimens were built with different ways of wrapping FRP sheets at the frame’s joints and both ends of beams and columns. The wraps were provided to prevent the peeling of the laminates this was aimed to investigate the effective ways of strengthening and repairing of the frame by applying different directions of CFRP and GFRP fibers. The analytical models are used to assess the efficiency of the FRP composites rehabilitation by comparison between intact and retrofitted specimens. Specimens were reinforced by FRP at the ends of beams، columns and at the joints; one specimen was not reinforced and was used for comparison. Also، the effect of laminate architecture، arrangement and type of material was considered. For achieving this purpose eleven models were analyzed in finite element model. The Finite element analysis results indicated that the choice of the Fiber composite materials، the laminate and wraps arrangement and thickness affected the enhancement of the structural joint performance significantly. The results provide an important insight of the role of FRP sheets in improving the earthquake resistance of frame buildings.